In late years, a CAD (computer-aided design) system incorporating CAD software in a computer is widely used in designing not only a product but also a die for molding the product. Taking a resin molding die for example, the CAD system is used to determine various design factors of the resin molding die, such as cavity configuration, parting line, component layout, cooling system.
The term “cavity” therein means a space formed in a molding die to receive therein an injected molten molding material such as resin and solidify the material therein so as to mold a product. While the cavity has a configuration analogous to that of a product to be molded, the product is practically molded with a different configuration from that of the cavity due to contraction caused in the molding material during its solidification. That is, it is required to determine the cavity configuration in consideration of contraction to be caused in the molding material. In addition, a striped strain or deformation, so-called sink mark, can be undesirably created in a product due to contraction caused in the molding material during its solidification. For preventing the sink mark from occurring, a cavity should be designed under the estimation of a cavity region causing a sink mark to allow a slightly increased amount of molding material to be supplied to the estimated region of a cavity for casting products or to allow a slightly reduced amount of molding material to be supplied to the estimated region a cavity for resin products. Typically, an engineer designs a cavity in a virtual space on a CAD system while conceptually constructing a 3-dimensional configuration of the cavity from 2-dimensional design drawings of a product in consideration of the contraction coefficient of a molding material to be used and an estimated cavity region causing a sink mark.
It is also required to divide the die into an upper-die-half and a lower-die-half by an appropriate plane to allow the product to be released from the die. The parting line can be defined as a line of intersection between the above plane and the cavity. This parting line is determined in consideration of an undercut of the product die and other factors.
If a product including an undercut portion or a lateral hole is molded only by a die consisting of an upper-die-half and a lower-die-half, it cannot be released from the die. In this case, a sliding core is essentially included as one of the components of the die. Thus, a layout design for determining the arrangement of the upper-die-half, the lower-die-half and the sliding core will be additionally required.
A die engineer designs a die through the aforementioned operations on a CAD system. The resultingly obtained CAD data can be used as a numerical control (NC) data. A metal machine tool has been automated to a considerable extent, and the obtained NC data can be entered into the machine tool to machine a metal material for a die.
While the conventional die design essentially includes various operations requiring skills for conceptually constructing a 3-dimensional cavity configuration of a die from 2-dimensional design drawings of a product to be molded by the die, and determining a die parting line and a die layout base on the determined cavity configuration, it is practically difficult for unskilled die engineers to master such operations in a short period.
In addition, a product-engineer's intention about a product configuration is not always expressed by 2-dimensional design drawings, and consequently a desirable 3-dimensional die configuration cannot be adequately specified from the 2-dimensional design drawings in some cases. In these cases, a die engineer must design a 3-dimensional die configuration while reasonably estimating the product-engineer's intention in accordance with his/her past experiences. Such an operation is not accomplished without a fairly high skill, and it is often the case that an unskilled die engineer keeps the operation going without awaking to inaccuracy in the design drawings, and consequently designs an erroneous die including an spatial inconsistency and/or an unattainable 3-dimensional configuration.
In the die design based on the above procedure, the die design can be initiated only after an associated product design has been completed. While a product engineer often desires to quickly verify whether an actual product is produced with performances identical to those intended in a product design, a considerable time-period is practically required to obtain a final or actual product after the completion of the product design, due to respective time-periods required for a die design and a die processing. In addition, a product design change after the initiation of the die design will be forced to re-design the die in conformity with the change, which leads to an extended time-period required for the die re-design and a more delayed timing of obtaining the actual product.
In the field of portable phones or the like where products have a short life cycle, and new products are continuously introduced into market, there is a strong need for reducing the time-period of a die design as well as the time-period of a product design.
If a product design change after the initiation of a die design includes an undercut likely to be overlooked due to simple checking of product design drawings, the fact can be found after the completion of the die design based on the design change in some cases. A product having an undercut causes an increased cost of an associated die and an extended time-period required for molding one product, resulting in sharply increased molding cost per product.